The Yale University Observatory announces the
publication of a completely revised and enlarged two-volume edition
of the General Catalogue of Trigonometric Stellar Parallaxes
containing 15,994 parallaxes for 8,112 stars published before the end
of 1995. In this Fourth Edition, 1,722 (27%) new stars have been
added to those contained in the previous edition by Jenkins (1963).
The mode of the parallax accuracy for the newly added stars (0.004"
s.e .) is considerably better than in the previous editions (about
0.016"). Approximately half of the newly added stars are fainter than
the Hipparcos Astrometric Satellite's magnitude limit of 13.0, while
approximately 2300 stars in The Parallax Catalogue are not in the
Hipparcos Catalogue.

Volume I contains a 29-page Introduction
describing the project and a summary of the analysis of the
accidental and systematic errors of the parallaxes. Those results
provide a "system" for the Catalogue which then yields weighted
absolute parallaxes for each star. Following the Introduction, on
each left-hand page a commonly used name is listed, along with the
equatorial coordinates in the system of the FK4 for 1900 and the
secular variation for 100 years to aid in quickly transferring from
1900 to 2000. Transit tables at the end of Vol. I are provided to
assist the user in locating stars with coordinates at the equinox of
1950 or 2000. The 1900 equinox has been maintained to avoid assigning
yet another star number. Following the coordinates, proper motions
are given along with the weighted average absolute parallaxes,
parallax error, number of parallax observations and a quality code.
The right-hand page adds the UBV photometry, MK spectral types, cross
identifications with the Bright Star Catalogue, HD, DM, CNS, variable
star name, ADS/WDS and another star name. An appendix lists the stars
in decreasing order of parallax.

Volume II contains for each star, all
published parallaxes, associated errors and sources of publication,
the average magnitude of the reference frame, galactic coordinates,
the correction to absolute parallax based on an improved model of the
Galaxy, absolute parallax and its error and the weight of the
parallax. The right-hand page contains a Section with the Notes to
the Catalogue, including additional cross-identifications, data on
the variability and binary nature of the stars, and other information
that might be of general interest. Another Section contains Double
Star information including the ADS number, the star's common double
star name, magnitudes of the components, separation and position
angle, and when an orbit is available, the semi-major axis and period
of the binary.

Printed copies of the Two-volume General
Catalogue are available from the Yale University Observatory, while a
condensed computer readable version of Volume I without the Introduction
and Appendices will be available soon from the Astronomical Data
Center (ADC) at Goddard Space Flight Center (also on a CD ROM disk
soon to be released) and from the Strasbourg Stellar Data Center
(CDS) in France. Volume II will not be available on the CD
ROM disk nor in computer readable form. A CD ROM disk was issued by
the ADC in 1991 which contained a preliminary version of the YPC. In
this final version we have revised the weighting system, and included
newly published parallaxes, photometry and spectral types for most of
the stars. The weighted mean parallaxes of many stars will be found
to differ from those in the preliminary version due to changes in the
weighting system, revisions to the default reference star magnitudes
and the addition of new data.